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ET: Engine (Twin) Rocker oil feed

gvw

Forum Website User
VOC Member
I’m after a bit of advice from you guys.

We noticed an oil leak on our recently acquired 1949 Rapide C.
The oil was coming from one of the rocker oil feed pipe connections.
On inspection our setup doesn’t appear standard.
The banjos we’re fixed with domed nuts rather than bolts and our ET100 feed bolt is nothing like shown on the parts list and is better described as a stud with an oilway cut into it with a sleeved nut attached - shown below.
9510F0A4-5768-44B0-9838-30D4E5CC2E34.jpeg


Can anyone shed any light on this - was this an original configuration that has now been supersede?
Can I replace the above with a standard ET100/1 and banjo bolt from the spares shop?

Thanks
 

Marcus Bowden

VOC Hon. Overseas Representative
VOC Member
Well my handsome, I don't honestly know what you have there. The original ET100 had a 3/8" BSF thread under a 1/4" hexagon bolt with an up standing threaded portion about 1/2" high and in it was tapped a 1/4"bfs thread that held on a cupped banjo doing each rocker assembly in turn. The bottom part of the 3/8" bolt has the lower four threads turned off and this portion is located into the aluminium rocker block. This was all superseded in the mid 60's with a mod that was the same but the 3/8"bfs thread was all machined off the the lower portion was threaded with 1/4"bfs thread and a special top had nut fitted while the rocker pin was removed and the hole in the rocker block top opened out to 3/8". On assembly the rocker is fitted the ET100/1 being screwed into it. What you have taken a photo of I've no idea it doesn't even look usable.
bananaman.
 

delboy

Well Known and Active Forum Website User
VOC Member
Yes, I have come across odd ones of these [as in your picture] in the past, but just changed them during he course of the rebuild for the locking version that we are all used to. They seemed to have been working okay.
Sadly, I never noted what thread was on the ones I binned, and can't remember what "nut" was in the rocker bearing.
Sorry, not much help.
Delboy.
 

gvw

Forum Website User
VOC Member
Well my handsome, I don't honestly know what you have there. The original ET100 had a 3/8" BSF thread under a 1/4" hexagon bolt with an up standing threaded portion about 1/2" high and in it was tapped a 1/4"bfs thread that held on a cupped banjo doing each rocker assembly in turn. The bottom part of the 3/8" bolt has the lower four threads turned off and this portion is located into the aluminium rocker block. This was all superseded in the mid 60's with a mod that was the same but the 3/8"bfs thread was all machined off the the lower portion was threaded with 1/4"bfs thread and a special top had nut fitted while the rocker pin was removed and the hole in the rocker block top opened out to 3/8". On assembly the rocker is fitted the ET100/1 being screwed into it. What you have taken a photo of I've no idea it doesn't even look usable.
bananaman.
we have also done quite a bit of head scratching
 

gvw

Forum Website User
VOC Member
Yes, I have come across odd ones of these [as in your picture] in the past, but just changed them during he course of the rebuild for the locking version that we are all used to. They seemed to have been working okay.
Sadly, I never noted what thread was on the ones I binned, and can't remember what "nut" was in the rocker bearing.
Sorry, not much help.
Delboy.

maybe a special by someone back in the day?
think I’m just going to order some standard et100/1’s and see if they fit?
 

chankly bore

Well Known and Active Forum Website User
Non-VOC Member
Well, the standard diameter on the shank of the ET100/1 is 5/16", so I'd first check what diameter the threaded portion of your "special" is. The next problem you may have is that the oil feed pipes might have been opened out on top to accept a thread of greater diameter than 1/4". What may help is a bolt used on the AMAL Monobloc carburettor which has a larger hexagon size with a sealing washer to suit. Part numbers are AM/376/091 and -092. Maybe you'll need new pipes. Using extended rocker bushes is also a good plan. The rockers should come out with a slide hammer and a small "U" bolt, but use soft metal on the pin you put through the tappet threads as they are sometimes brittle. When you come to final assembly remember to tighten the oil unions onto the cylinder head before tightening up the union nuts, 234. In my mechanically illiterate opinion, dome nuts, to quote Molesworth, are a BAD THING.
 

Bill Thomas

Well Known and Active Forum Website User
VOC Member
Yes it looks like the Rockers will have to come out,
To see what they have done to the top of the rocker bearings,
I did my own mod' on the locking type in the 70 s,
And used a wider thread than is now supplied !.
There were a few different ways of stopping the rocker bearings from moving,
Back years ago,
But the best one is what the club now supplies,
But you MAY have to grind a bit of metal away from top of the rocker ARM,
If you look at the NEW rocker arms supplied now, You will see where you have to grind,
A bit away, To allow full movement .
Good Luck, Bill.
 

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Vincent Brake

Well Known and Active Forum Website User
VOC Member
Look up the special tool needed before you hit the rocker bearing pin out with a Hammer.

Order some new alu bearings beforehand!!
 

chankly bore

Well Known and Active Forum Website User
Non-VOC Member
Er, the rocker pins are pressed out, perhaps you misunderstood me, sport. A slide hammer on the tappet end of the rocker should be safe given my previous caveat. Just don't touch the large thread on the inspection cap holes.
 

bmetcalf

Well Known and Active Forum Website User
VOC Member
But you MAY have to grind a bit of metal away from top of the rocker ARM,
If you look at the NEW rocker arms supplied now, You will see where you have to grind,
A bit away, To allow full movement .
Good Luck, Bill.
Didn't Ian or someone say in a thread that the grinding shown is more than necessary? Also, careful polishing is needed to avoid any stress increasing grinding marks.
 

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